The present invention relates to methods for preparing coatings through enzymatic reactions with components of wood. More particularly, the present invention relates to the enzymatic polymerization of lignin based compositions with phenol oxidizing enzymes.
It has been estimated that nearly 20% of the chemical pulp and dissolving pulp provided worldwide is produced by the sulfite process. Moreover, the significance of this process has grown with the large-scale employment of modifiable magnesium bisulfite pulping. Nonetheless, although there exist a number of uses for lignin sulfonates produced by these processes, it has been difficult to find commercially feasible and desirable means of disposing of this large waste stream for useful purposes. As described in U.S. Pat. No. 4,432,921, the use of spent sulfite liquor as an adhesive for paper, wood and other lignocellulosic materials is well known in the art, and is facilitated by enzymatic activation of the lignin using a phenol oxidizing enzyme. U.S. Pat. No. 5,505,772 describes a method of preparing particle boards by conglutinating wood fragments having middle lamella lignin with a phenol oxidizing enzyme, the process having the advantage that it is necessary to add no additional binder. Further, it has been shown that laccase and other oxidoreductase enzymes, such as peroxidases, can be used as polymerization or curing catalysts for lignin (PCT Publication No. WO/98/31761; EP 648 242).
PCT Publication No. 93/23477 discloses the production of a solution or gel of lignin at high concentrations free of solids by treating the lignin at a high pH and then lowering the pH to a desired value. A binder can be made by subsequently treating with a phenolic oxidase.
PCT Publication No. 95/07604 discloses a method of producing fibreboard, the method comprising the sequential steps of (a) providing an aqueous slurry or suspension of lignin-containing wood fiber material; (b) adding a phenol oxidizing system to the fiber slurry; (c) forming the fiber slurry into a mat of the wood fiber material; and (d) pressing the formed mat by applying heat and pressure to produce the fiberboard.
PCT Publication Nos. 98/31761, 98/31762, 98/31763 and 98/31764 further disclose lignin based adhesives and methods of producing such adhesives for the production of fiberboards.
PCT Publication No. 98/31728 discloses intermediates for the production of polymers from lignin derivatives from the pulp industry, produced by processing lignin derivatives with phenol oxidizing enzymes in the presence of oxidation agents. The invention is characterized in that the lignin derivatives are (a) subjected to enzyme treatment for more than 3 hours in the presence of air; (b) subjected to enzyme treatment for more than 10 minutes while air or oxygen is passed through them; or (c) are oxidized by treatment with chemical oxidation agents. The intermediate is used for the production of polymers of lignin derivatives from the pulp industry, of fiber reinforced duroplastic composite materials from plant fibers, of water proof papers and cardboards, as well as duroplastics from lignin derivatives.
Thus, there has been much activity in the field of using phenol oxidizing enzymes to produce adhesives from lignin. However, other uses of lignin and sulfite spent liquors are necessary to economically dispose of the large quantity of waste material produced by the pulp and paper industry.